It is desirable to have means in connection with an inboard-outboard type of boat to propel the boat at a speed slow enough to be suitable for fishing as by trolling and the same is referred to as a trolling speed.
It is not desirable to attempt to slow down a power unit in a boat designed for traveling speeds to a slow speed such as for trolling purposes.
The following reference material is cited as being representative of the development of art which is known. In U.S. Pat. No. 3,756,186 an auxiliary motor is used by exchanging positions with the main power unit. In U.S. Pat. No. 3,881,443 a small electric motor powered propeller is lowered into the water to drive the boat for fishing purposes. In U.S. Pat. No. 3,596,625 a pair of auxiliary motors are mounted upon the transom of a boat to drive trolling propellers. In U.S. Pat. No. 2,504,833 a smaller power source is used to drive the main propeller in place of the main power source, for fishing purposes. In U.S. Pat. No. 3,139,853 an auxiliary motor is mounted upon the cavitation plate of the main motor and utilizes a separate power source for propulsion. In U.S. Pat. No. 3,587,512, a shaft is lowered into the water carrying a unit to propel a boat at fishing speeds. In U.S. Pat. No. 3,601,980 a hydrofoil is disclosed having an auxiliary power source to drive an auxiliary propeller to attain lower speeds. Here separate engines are used and may be coupled to drive the main propeller and there is no simple control member which selectively causes either the main propeller or the auxiliary propeller to be powered to drive the boat.
The structure disclosed and claimed herein represents substantial improvement in providing a trolling propeller mounted in position for operation without requiring any change of position of itself or of the main propeller with respect to the boat and in utilizing the main power source through driving means reducing the power output for suitable operation of the trolling propeller at a fishing speed.
It is an object of this invention to provide a trolling propeller as an attachment to a main propeller assembly for a selective independent operation as an alternative to the main propeller without any manual change of the positions of the propellers.
It is another object of this invention to provide means for operating a boat at trolling speeds utilizing the main power source and not requiring a relative change in position of the main propeller with respect to the boat.
It is a further object of this invention to provide in connection with an inboard-outboard type of motor boat a trolling propeller carried by the main propeller assembly without requiring any relative adjustment of the positions of each other and to utilize selectively in the alternative with the main propeller, the main power source.
It is more specifically an object of this invention to provide a trolling propeller removably attached to a main propeller assembly and having power transmission means connected to the main power source for use selectively of said main power source for propulsion in the alternative with the main propeller and in operation requiring no relative adjustment as to position of the trolling propeller or the main propeller.